Telephone system



Dec. 1, 1931. H M, FRIENDLY 1,833,991

TELEPHONE SYSTEM Filed Oct. 21, 1921 9 Sheets-Sheet 1 Dec. 1, 1931. H. M. FRIENDLY TELErH'oNE SYSTEM 9 Sheets-Sheet 2 y [U m DS Filed Oct. 2l, 1921 Dec. 1, 1931. H. M. FRIENDLY 1,833,991

' TELEPHONE SYSTEM Filed oct. 21, i921 9 sheets-sheet 5 imm 9 Sheets-Sheet Filed Oct. 21, 1921 d.. n Cd Invenf nr Herb EF1-Hmm De@ 1, 1931 H. M. FRIENDLY 1,833,991

TELEPHONE SYSTEM File c .N21, 1921 9 sneetsLsnex 5 'u 9j Il l Y Ln MBS Dec- 1, 1931- H. M. FRIENDLY 1,833,991

TELEPHONE SYSTEM Filed oct. 21, 1921 9 sheets-sheet e /Wy/My Dec. 1, 1931. H. M. FRIENDLY TELEPHONE SYSTEM Filed-Oct. 21, 1 921 9 Sheets-Sheet '7 NQ WN* @MM s h k Y 9 sheets-sheet s Inverlnr' non. Y ,N

Dec. l, 1931. H. M. FRIENDLY TELEPHONE SYSTEM 9 Sheets-Sheet 9 Filed oct. 21, 1921 Invennr l HErher-FI-Frendlg WY Aims DEL.

Patented Dec. l, 1931v UNITED .STATI-:s

PAPIEIN'P oFFICE i HERBERT M. FRIENDLY, F PORTLAND, OREGON; HILTON S. FRIENDLY AND CENTRAL TRUST COMPANY 0F ILLINOIS E XECUTORS OF CEASED sm Eliminar u. rnrnn'nnr. pr:-

TELEPHONE SYSTEM Application tiled October 21, 1921'. Serial No. 509,263.

The present invention relates in general to automatic telephone systems, and is particularly adapted to a s stem that includes a main exchange having a ranch exchange tributary to it.

More specically,theinventionrelates to an improved method and apparatus for permitvting connect-ions to be passed, transferred, or extended successively from station to station in a connection primarily established from a calling telephone to a first called tele hone, the calling telephone being directly tributary to the said main exchange, and the called telephone being tributary to a said branch exchange; the latter known in the art as a private automatic exchange, located on the premises of a subscriber, and involving a plurality of telephones related for automatic interconnection, and for incoming and outgoing service with the main exchange over one or more trunk lines.

' Other systems have been invented which contemplate certain functions of this nature. However, the present invention contemplates A additional novel functions, together with improvements in the structure, and operation of such a system consistent with realizing the novel functions. l

Heretofore, so far as I am aware, call connections which are enabled to be passed within the private automaticexchangemust have been originated from without, and extended over a trunk line from the main exchange to terminating equiments in the private automatic exchange, and thence to desired called stations within the private automatic exchange, directed from the calling station, or from a called station, or possibly from either the calling or a called station, as preferred. A salient object of the present invention is to not only enable calls to be completed to the private automatic exchange, and then passed from station to station, but to allow calls originating within the privatel automatic exchange to be completed over a trunk line to the main exchange and thence to a station therein, and forthwith thereafter pass the connection at the calling end. For example, an attendant or other party at a station within the private automatic exchange will directly establish a connection to a desired party in the main exchange and thereafter pass the calling connection at the private automatic exchange end to a successive station, the operative details, so far as the users are concerned, are as if the call had been extended from the main exchange to the calling station in the private automatic exchange in lieu of the call having'been extended from the private automatic exchange to the main exchange.

From the foregoing general statements it will appear that the present invention contemplates that outgoing and incoming calls are resolved into the same service relation at the private automatic exchange so that supervision, operation, and service is the same, regardless of whether a call is outgoing or ins coming. Moreover, the present disclosure shows means wherein th same trunk termi- 7o nating equipments at the private automatic exchange is brought into requisition in pass` ing connections, regardless of which end ofy -the trunk is theoriginating end.

In general, the novel operationof the present invention is as follows: On calls originating in the main exchange the first available trunk to the private .automatic exchange is attained by operating an automatic calling device whereby the call is directively extended from the calling telephone through the selectors to a connector having access to .the private automatic' exchange trunks, in away generally well known, the connector, -however, being novel and has novel operative g5 functions as will appear presently..i ,',Upon the 'first disengaged trunk being seizedthe trunk terminating equipment at the lprivate automatic exchange end is caused to automatically function and thereby extend the trunked connection to a iirst available telephone in the private automatic exchange. In this connection it is to be borne in mind that a predetermined attendants telephone in the private automatic exchange is to be normally the said first available telephone, but in case this telephone is engaged, by reason of it having been called through some other trunk terminating equipment acceible to it, or that it is engaged in a local or in an out trunked i different party.

e 1,883,991 e connection, the trunk terminat" equipfunctioned its shaft on its normal level, y ment will'select and seize a line leg to an is now capacitated to function its shaft verwhich latter maybe in physical reach of the party answering calls at said rst available telephone, or -be at a remote location therefrom, responsive to a- The party at the called tele phone responds by removingl the receiver rom the switch-hook, or by manipulating a key (equivalent to a switch-hook, but not shown) t0 include the telephone invseriesrelation with the line leading thereto.

In the exampled instance, the trunk terminating equipment at the private automatic.'v exchange end of the trunk consists ofvtwo companion interlinked switching elements. One ma be termed the main elementv and the other tlie auxiliary element thereto.- The main element primarily automaticallyfunctions as a group selecting connector 'on its normal level consequent to the seizure of the trunk at-the main exchange end. However, upon the releasing of its shaft to normal, without releasing its leading-in trunk at the main exchange end, the shaft of the said main element is thereafter capacitated'to be operated vertically and then horizontally, directively. v

It will now be assumed that a trunk has been seized at the main exchange end and that the main element at the private automatic exchange end of the trunk automatically extended the call to the first available telephone and signals it. The party thereat after responding, ascertains what local telephone is wanted. party will then manipualternative telephone,

The said 'late the callingdevice of the telephone operative to the said auxiliary element, whereby the line extending to the desired telephone is seized (if not busy) and signaled upon.l The said party may restore the lshaft of the auxiliary element at any time before a. response is obtained therethrough, directively, or in case the desired line is found busy to efface response is the extended connection and', 'if desired, extend the call to another telephone. The said partyl may retain connection until after a obtained, and in fact, remain in conference relation with the calling and last called party, unless directively released by the last called party, or by voluntarily replacing the receiver on the switch-hook. If the first called party replaces the receiver before a response is obtained, the said party may remove'y it and come in onthe connection not responded to and re-communicate with the calling party in the main exchange. If desired, the shaft of the auxiliary element may be released and the call re-extended through it to some other telephone. However, if the wanted party responds, after the first called party has replaced his receiver, the shaft of the main element will thereby be restored to normal, disconnecting the first. telephone reached. The'main element,'which l the calling device of the telepv nection as primarily Ying party, and the last called responsive to one last called, the auxiliary tically and then horizontall and which was reached through element, and in general, operate like the auxiliary element, which does not have a normal rotary shaft movement under any condition.

If the calling party `in the main exchange desires to directivelyextend the trunked conextended to the first available telephone through the normal level of the main element, the said calling partywill forthwith annex the digits correspond. ing to the wanted telephone, whereupon the auxiliary element will extend the connection thereto and apply signaling current. A novel feature of the present invention is a means for delaying the application of signaling current to a line first seized by the main element, so if the calling party in the main exchange immediately annexes the digits Corresponding. to the specific station in the private automatic exchange-wanted, reached through the auxiliary element, the main element will be incapacitated against project ing signaling current before .it vis timed to project it. In any event, the first directive impulse applied to the auxiliary element incapacitates the main element'against apply-l ing signaling current. The shaft of the main element is restored` consequent to the specific station responding.

A meansis provided for reversing the direction of current projected towards the main exchange from the line rela of the main element upon a first response being attained in the private automatic exchange, and this reversed condition is maintained until the shafts of both the main and auxiliary elements are restored to normal, regardless of the condition of any local which either element may be connected.

A means is provided wherein-a tone source is briefly applied when a call has been passed and reslponded to, and the passing party has not rep aced the receiver on the switch-hook before the response is obtained. This is to prompt the last respondingv party that a local station is in talking relation tothe connecline to tion. A conference may proceed between the calling party in the main exchange,lthe passparty, or either one of the latter two may voluntarily replace the receiver on the switch-hook, or either of the locallines may be disconnected directively from the alternative local line, as desired, f

whereupon a brief tonewillbe agaln applied. Calls originating at thev private automatic exchange destined to a telephone in the main exchange are effected 'through the agency of a local connector operating as a selector'on its O level, and there seizing ay trunk to the Y main exchange. Upon the connector seizing,

the main element at the private automatic exchange end of the trunk selectively operates its shaft on its normal-level and seizes the first set of bank contacts, which corresponds to the extension from the local connector. Then, upon a response of the called party in the main exchange, a relay disconnects the connector from the trunk and at the same time alternatively connects it to the trunk through the main element. It also causes the said trunk to be continued to the main and auxiliary elements in the private automatic exchange, so that in lieu of the primary connection from the 0 level of the 1ocal connector extending directively to themain exchange over the trunk, the trunk is now reached through the 0 level of the local connector and the normal level of the Vmain element, and through the main element to the trunk. Upon the shafts of the main and auxiliary elements being restored, the trunk will be opened sufficiently long to restore the linking switches in the main office. If the called partv in the main exchange disconnects first, the main or auxiliary element, or both of them, if off-normal, will be restored so that the operation so far as the users are concerned is essentially as if the call had been made to the private automatic exchange from the main exchange. The local telephones in the private automatic exchange are enabled to pass calls after gaining the response of the called party in the main exchange as if the call originated within the main exchange.

From the last foregoing, it will appear that a party at any stance of a party at some other telephone in the private automatic exchange, may call a telephone in the ,main exchange, and thereafter pass the connection to the telephone of the instructing party (or other telephone), from whence it may be further passed, as if the call had been an incoming call to the private automatic exchange primarily.

Means is provided so when a call is initiated at the private automatic exchange whereby thel call from a telephone therein is directively extended to a first selector in the main exchange, and thereafter directively extended to a called station in the main exchange, if the called party in the main exchange terminates an established talking connection by replacinO the receiver on the switch-hook thereat while the calling party still maintains the receiver at the calling station off the switchhook, the trunk and linking apparatus in the main exchange will be restored to normal, and, therefore, a new call initiated at the main exchange can be forthwith extended over the said trunk, or any other available trunk, into the private automatic exchange. This, of course, will imply that the lineswitch terminating the trunk at the main office will not plunge-in under this condition.

telephone, perhaps at the in' The private automatic exchange equipment associated with the trunk line leading from the main exchange is generally adapted for use where the main exchange is operated manuallyv rather than tively over the trunk line from the private automatic exchange. It will thus appear that where a private automatic exchange is installed in connection with a manual main exchange and that the mainexchange is later displaced by an automatic main exchange, only a slight circuit modification is necessary to adapt the trunk terminating equipment at the private automatic exchange to the changed method at the main exchange end of the trunk. y

Where the private automatic exchange trunk is connected to a manual exchange, and a connection is directively established from the private automatic exchange over the trunk, and thence through an answering springj ack and co-operating cord pair of the main exchange, and the service is terminated first at the main exchange end by the operator thereat withdrawing the switching plug from the trunkspringjack, the connection will be destroyed and a false call will not occur at the main exchange end, and the trunk may be used forthwith for outgoing service from the main exchange. l

Under the last above condition, clearing supervision will be afforded the operatorat the main exchange, operative in the `event the calling party from the private 'automatic exchange terminates the service first.

The foregoing specifically mentioned functions of the present invention and other functions and features thereof believed to be novel will be discussed hereinafter.

Referring to the drawings Fig. 1 is a subscribers telephone leading into a main exchange, together with a lineswitch and a first and a second selector adapted to extend a connection in the direction of a called line. A connector adapted to complete a connection to the line leading to the said subscribers telephone is shown, together with preceding selectors adapted to be interlinked therewith in establishing the connect1on.

Fig. 2 shows a connector of the present invention and an incoming lineswitch associated with one of the lines accessible to the said connector.

Fig. 3 shows auxiliary apparatus at the private automatic exchange end' of a trunk connecting. the main exchange and the private automatic exchange.

Fig. 4 is a main element J of a pair of trunk terminating switch elements of the present invention.

Fig.l 5 is an auxiliary element K to the said main element.

Fig. 6 is a connector which will function as a selector on certain levels, and has other automatically direc' lum functions Well known, as well as of the present invention.

Fig. 7 shows a portion of the main element J of Fig. 4 and two local telephones.

Fig. 8 shows a portion of the auxiliary element K of Fig. 5 and two local telephones and line switches therefor.

Fig. 9 shows the manner in which the accompanying sheets are the complete automatic system contemplated in the invention. The lines extending towards the margins and registering with lines on other sheets when placed in the indicated relation are to be assumed as continuations of the same line, though not designated by functions reference characters, the latter being omitted trunk through a springjack where possible Without obscuring the clearness of the complete disclosure, with due reference to the prior art and its relationship tothe devices of the present invention.

Fig. 10, which attaches to the left-of Fig. 3, alternately with Fig. 2, shows well known manual exchange equipment such as has been widely used in terminating private branch exchange trunks in main oiiices of manual systems. together with a well known switching cord pair Q adapted to connectwith the and extend the connection to or from the springjack of an accessible line. Fig. 11 shows an alternative relay for excluding a resistance from the battery side of the trunk in lieu of reversing the trunk. ln

the event the main exchange is manual, in lieu vof automatic, the Said Fig'. 11 will be introduced in main element J of Fig. 4 where indicated by the section lines a, b, and c.

Fig. I2 shows the manner in which the accompanying sheets are assembled to dis- 40 invention under the operation, wherein the main exchange is operated manually, reference being made to the play the complete svstem contemplated in the alternative method of in lieu of automatically, statementsmade in connection with Fig. 9.

" In embodying the present invention in a are employed which system -as contemplated, apparatus elements are well known in the art. For example, the subscribers telephone and others not shown) in the main exchange may be'of the same class, and, in fact, of the I exact' type as thetelenhone designated A in U. Patent No. 13,901, re-issued to Frank Newforth, April 13, 1915. To extend aconnectionv from telephone A in the direction of a called line, lineswitch C will function upon initiatino' the calland automatically extend lthe'connection to first sclector'E. Upon mamatic exchange,

nipulating the calling device at the calling A.telephone A in accordance with the first digit 1 of called' number l1-11 corresponding to the' group of trunks to the erate responsive thereto and seize a trunk leading to second selector F. Upon operatassembled to display private autothe first selector E will oping the said calling device in accordance with the second digit 1, selector F will operate responsive thereto and seize a trunk leading to the connector G in Fig. 2. In order not to unduly involve the descriptions, the lineswitch C and the selectors E and F have been indicated rather than detailed, as well known forms of these elements may be employed. In fact, said C, E, and F may be of the exact types designated C, E, and F respectively in the said cited patent to Newforth.

Referring to Fig. 2, vit will be clear pres-v ently that the-connector G (which belongs to the general class as H of the said cited patent to Newforth) is agroup-selecting conlnector controlled vertically and-rotarily by and which disassociatcs its (line relay windings) from the normal bridge relation, consequent to the connector seizing.` The connector G has access by` first choice to a trunk vof a group leading to a privatev automatic exchange, terminated by the equipments shown in Figs. 3, 4, 5, and 6. The said trunk is designed fortwoway service in the present exampled system, though it will be manifest that trunks employing the present invention may be reserved for one-way service only. The said trunk has a lineswitch C permanently associated with it at the main exchange end. The lineswitch will operate and automatically extend the trunked connection to `first selector E upon a conductive path being cl'osedbetween the limbs of the trunk, or upon the battery lside of the trunk becoming grounded or applied tobattery potential of the oppodirective impulses operative circuits site polarity.

` the calling device in accordance with the final two digits 1`1 will cause the connector to seize and signal upon the line leading to said A.' While other well known forms of selectors, connectors, and lineswitches can be 12C substituted for the said elements in Fic'. 1

D 7 indicated only, in order to simplify the disclosure, the lineswitch C', selector E', selector F', and connector H', may be assumed of the exact types as C, E, F, and H, respectively, 'in the said cited patent to N ewforth.-

Attention is directed to the 'fact that conncctor in the said cited patent to N ewforth causes the current projected vovervits leadinginline conductors tobe reversed in direction l consequent to a' response being obtained on the called line. That is, when the called party responds the current traversing the calling line is reversed in direction consequent thereto. This reversal of currrent may be used for supervisory and other uses, but it will appear presently, this condition is herein employed for the novel purpose of causing circuit changes affecting the relationship of thel calling line to the trunk on calls outgoing from the private automatic exchange, to the main exchange.

In order toy more conveniently correlate the elements in Figs. 1 and 2 to the corresponding elements in the said cited patent to Newforth, conductors and parts in Figs. 1 and 2 corresponding to conductors and parts in the said cited patent to Newforth will be similarly designated. In order to avoid confusion, designations with reference to E and F have a prime added. y

Figs. l and 2 thus clearly disclose a main exchange system wherein a call may be initiated from a telephone therein and extended therefrom to a first selector automatically through the agency of a lineswitch, and then directively extended through a second selector to a group-selecting connector, and likewise through the said connector to a first available trunk of a group extending to a private automatic exchange system on the premises of a subscriber. Figs. 1 and 2 also clearly disclose a means of extending a connection, initiated over the said trunk and extended therefrom to a first selector automatically, through the agency of a lineswitch in the main exchange, and then directively extended through a second selector to a connector, and likewise through the said connector to a line leading to a telephone. In fact, Fig. 1, and also Fig. 2, with the exception of novel details and functions incorporated in connector G thereof, sets forth a well known organization of well known equipments constituting a main exchange system. The present invention is, however, particularly directed to a novel organization forming a private automatic exchange which is co-ooerative with the said well known organization constituting the main exchange, correlated through the agency of the novel connector G in the main exchange for calls de-'tined to the private automatic exchange.

Referring to Figs. 4 and 5. the elements J and K are of the general class shown in Figs. 9 and 10, respectively, of British patent to Friendly (the present applicant) No. 139,000, the circuits of which are modified in accordance with the present invention.

Referring to 6, the connector L which is well known in the art, with the exception of certain holding features, as will appear, belongs to the general class as set forth in U. S. patent to Deakin, No. 1,164,479, granted December 14, 1915.

Referring to Figs. 7 and 8, the lineswitches M, N, O, and P, are of the general class as set forth in U. S. patent to Lamb, No. 1,193,160, granted August 1, 1916, and is well known in the art. The telephones or substations T7, T7 T8 and T8', are of the same class as A in Fig. 1.

To simplify the drawings and descriptions, the battery (which has its negative pole grounded), and ground are shown as independent sources throughout, wherever applied, but it is to be understood that the system is of the common battery type, and, therefore, one only or a lesser number of sources may be employed than indicated. In the descriptions, when a circuit is traced to a winding, the opposite terminal of which is shown applied to grounded battery or to ground, the described circuit is to be considered as traced to ground through the winding and battery, or'direct to ground, as indicated. In this connection, attention is directed to the connector H of the cited patent to Newforth, wherein line relay 16 has its battery winding normally connected to the conductor leading to vcondenser 30, and has its ground winding normally connected to the conductor leading to condenser 31, that is to say, conductor 58 and conductor 59 in Fig. l will normally have battery and grouid potential connected to them through a re a borne 1n mind that the said cited patent fully discloses that the above referred to battery and ground windings are reciprocated with respect to the talking conductors leading in to the connector, incidental to a response being obtained on the called line.

The operation of lthis improved system will now be described in general, by tracing and discussing its functioning under different assumed operative conditions.

winding, respectively. It will be Assume a call from telephone A to the private automatic exchange, the telephone number of which is 1111. Upon the calling party initiating the call by removing the receiver 2 from the switch-hook 4 the lineswitch C will plunge-in and seize the first selectorl E. Upon sending the first digit 1,, constituted of one open impulse, the selector E will respond by stepping its wipers into alignment with the first level of bank contact-s thereof and automatically rotate-in thereat and seize the first disengaged trunk actuate one time responsive thereto, armature 206 applying its ground to armature 209, series winding of slow-releasing relay 210, to the vertical magnet V2, sideswitch wiper 212 to grounded battery, relay 210 actuating and the vertical magnet stepping the wipers 213, 11', 12', and 13', into alignment with the first-level o f bank contacts thereof. At the time relay 210 actuated. armature 215 applied its dground to conductor 216, operatively energilzing interrupter relay 217 and private magnet 218W` Upon relay 210 deactuating,

following the impulse to the vertical magnet, causing the armature of theprivate magnet 218 to retract` sideswitch wiper 212 and its companion sideswitch wiper 219 will be permitted to advance into their second position, the connector being now in readiness to receive the fourth digit. party sending the fourth digit 1 relay 201 will again deactuate and re'actua-te one time responsive thereto, armature 206 applying its ground to armature 209, series Winding of relay 210, armature 220, winding of the rotary magnet R2, sideswitch wiper 212,v ,to grounded battery, actuating the rotary magnet to step the wipers vin one rotary position into engagement with bank contacts 221 to 224 (inclusive) respectively. .Upon the relay 210 actuating, energized in series with the rotary magnet. the relay 217 and the private magnet 218 will be operatively energized in the manner as before set forth, and when the relay 210 deactuates following the impulse to the rotary magnet, the armature of the private magnet will retract, permitting` the sideswitch wipers 212 and 219 to advance into their third position. A circuit can now be traced from grounded armature 206, sidev212 to grounded battery. relay 227l actuating.

switch wiper 219, winding of slow-releasing The circuit path'traced from the calling telephone A to talking conductors 58 and 59 is nowcontinued from conductor 58, .armature 202, winding lof slow-releasing shunted relay 230, wiper 12', bank contact 223, conductor 84. armature 301, conductor 302, conductor 303, armature 304, make-before-break spring 305, conductor 306, make-before-break spring 401, conductor 402 to the upper winding of line relay 403, and from the lower wmding of-said relay, conductor 404, makeslow-releasing relay 205 to' Upon the calling Y lbefore-break spring 405, conductor armatu re 307, con" uctor 83', bank contact 224,

Awiper 13', armature 203 to conductor 59, re-

will depend uponthe-actuated condition of relay 230, which inturn, depends uponthe continuity of the traced circuit including the windings of relay 403. That is to say, if the described circuit including the windings of the relay 403 is opened, relay 230 will deactuate consistent with its slow-releasing characteristic, whereupon relay 205 will deactuate, removing the ground from conductor 91 and from the lowervwinding terminal of relay 227. Relay 227 is adjusted so it will deactuate after relay 205, andthe relays maintaining lineswitch C and selectors E and F will also deactuate, causing the said C, E, and F, to restore in the well known manner. A circuit can now be traced from armature 208,

spring 237 of off-normal set 0N2 (which set operates on the first off-normal movement of the shaft) armature 238 to the release magnet Re2, the release magnet operating to restore the shaft of connector G to normal.

Assuming that at the time the wipers 213, 11', .12', and 13, engaged bank contacts 221 to 224 respectively, bank contact 222 constituted ground potential due to its corresponding trunk being busy by reason of the lineswitch C'v being plunged-in, or becausev of the trunk having been previously seized by a switch having common access with G to the said trunk, it being clear that when a connector seizes and its-conductor corresponding to 233becomes grounded as described, the bank contact corresponding to 222 seized will constitute ground potential. vThe ground encountered by Wiper 11 will ybe `conducted over conductor 233, sideswitch wiper 219 to 216, causing relay 217 to actuate and interrupt the circuit traced energizing the rotary magnet and also to maintain the private magnet attracted. Upon the armature on the rotary magnet retracting, and relay 217 deactuating consequent thereto, the before traced circuit through the winding of the rotary magnet Will'becomc closed to ground on armature 215, provided bank contact 244 constitutes ground potential due to its corresponding trunk being busy, and in that event the said wiper set will be advanced into engagement with bank contacts 247 to 250 respectively, these being the bank contacts of the third trunk of a group of trunks extending to the private automatic exchange concerned. Assuming further that when the wipers have been advanced as last stated that bank contact 248 constitutes busy ground potential, bank contact 247 lwill likewise constitute ground potential, due to their being electrically tied together by tie conductor 251. At the time wiper 2.13 engages grounded bank contact 247 a circuit can be traced from grounded bank contact 247, wiper 213, conductor 252, make-before-break spring 253, conductor 254, armature 255, winding of relay 256, sideswitch wiper 212 to grounded battery, relay 256 actuating and locking through said spring 253, armature 258, conductor 259 to 'grounded off-normal spring 260. Relay 256 cannot unlock unless spring 260 is disengaged, which can only occur upon the shaft restoring to normal, and, therefore, the switch will not seize after relay 256 is actuated notwithstanding ground is removed from bank contact 247 by reason of the trunk becoming idle. From the foregoing it is manifest that whenever wiper 213 encounters ground, the group selecting functioning of the connector G ceases, and by reason of armature 265 being attracted, ground-seeking busy tone from source T2 is applied to conductor 59, audible to the calling party.

From the foregoing description relating to connector G it is manifest that the said connector does not project ringing or signaling current to the seized trunk, nor does it supply talking battery to the called and the calling line as is usual in connectors. It will also be manifest that the connector G in its seized state involves no bridged attachments, and that the talking circuits thereof are clear, upon the connector seizing. Further, that the said connector is dependent upon other switch elements for its restoration to normal, all of which are novel so far as I am aware.

The system choserLto elucidate the present invention, so far as thel private automatic exchange is concerned, involves a single trunk line, although it is to be understood that in commercial installations there would usually be a plurality of trunks terminating in the private automatic exchange, each having equipments similar to the equipments on the trunk illustrated, so we are concerned chie with the trunk leadin from the first set o bank contacts accessib e to connector G, constituted of conductors 84 and 83.

Going back to the condition of the circuits at the time relay 403 was described as actuating, a circuit can be tracedfrom grounded armature 407 to the winding of slow-releasin relay 408, causing it to actuate. A circu1t can now be traced from grounded armature 409, conductor 410, armature 411, con-- ductor 412, Winding of slow-releasing series relay 413, conductor 414, armature 415, winding of rotary magnet R4, conductor 416, armature 417, sideswitch wiper 418 to grounded battery, the rotary magnet operating to advance wipers 701 to 704 one rotary step into engagement with bank contacts 705 to 708 respectively. Incidental to this first rotary off-normal movement, olf-normal springs R04 operate. Also, the armature on the rotaryv magnet applies the ground on its working contact to conductor 419, operatively energizing interrupter relay 420, and the private magnet P4 by its outer winding. At the time the rotary oH-normal springs R04 operate ground is applied through them to the winding of relay 421, causing it to actuate. A locking circuit can be traced from this Winding, armature 422, conductor 423 to grounded armature 424 of actuated relay 408. At the time the armature of the rotary magnet R4 retracts, deenergizing relay 420 and the private magnet P4, sideswitch wiper 418 and its companion wiper 425 are permitted to advance into their second position. In this connection it will be noted that grounded armature 308 applies its ground through its resting contact to conductor 309 and to bank contact 706, engaged by wiper 702, and therefore, a circuit can be traced from the grounded bank contact 706, wiper 7 02, conductor 426, sideswitch wiper 425 to the inner winding of the private magnet P4, maintaining it energized, although the ground has been removed lfrom conductor 419 incidental to the retraction of the armature on the rotary magnet R4. A circuit can now be traced from grounded armature 427, armature 428, armature 429, conductor 414, armature 415, winding of rotary magnet R4, sideswitch wiper 418 to grounded battery, the rotary magnet operating to advance the wipers 701 to 704 a rotary step into engagement with bank contacts 709 to 712 respectively. lIt will be as sumed that bank contact 710 does not constitute ground potential by reason of the line leading to telephone T7 being idle, and, therefore, the inner winding of private magnet P4 is deenergized, and the outer winding thereof is also deenergized by reason of the retraction of the armature on the rotary magnet R4 consequent to the rotary magnet circuit being opened by the interrupter relay 420 at the time the rotary magnet armature attracted. The private magnet retracting 4permits the sideswitch wipers 418 and 425 to advance into their third position. A circuit can now be traced from ground, sideswitch wiper 425, conductor 426, wiper 702 to engaged bank contact 710, which will guard the line leading to telephone T7 against intrusion through other switches (not shown) having access to bank contacts multiply related to it. This lground can also be traced from sideswitch wiper 425, winding of seizing relay 430, sideswitch wiper 418 to grounded battery, relay 430 actuating by way of. accomplishing the seizure of main element J. Interrupter I4 has a plunger with a retarded movement for closing the ringing circuit from source G4 to armature 431. That is to say, the said circuit from the source G4 is not closed for a predetermined period, which may be adjusted to suit conditions, after the winding of the interrupter I4 is energized.

' This latter winding will be energized consequent to the actuation of relay 408 incidental to the trunk to the private automatic exchange being seized, due to armature 424 grounding conductor 432. The period of retardation of interrupter I4, for example, would be five seconds under general operating conditions and, therefore, at the expiration of that period, which isa longer period than is required for the wipers 701 to 704 to have rotated the two steps into engagement with bank contacts'709 to 712, respectively, and, therefore, the ringing circuit will not be completed and operative for an appreciable time after the seizure, the object of which has been set forth in the general remarks at the outset and which will be discussed morein detail presently. The ringing circuit may be traced from source G4, left contact of interrupter, its short circuiting bar and the right contact, armature 431, armature 432, conductor 433, wiper 703, bank contact 711, conductor 714l through the ringer of the telephone set T 7 conductor 715, bank contact 712, wiper 7 O4, conductor 716, armature 434, armature 435, inner winding of ring-cut-off relay 436 to grounded battery. The current traversing the last traced circuit is operative to the ringer at telephone T7, but is inoperative to relay 436. Upon the response, wherein the receiver is removed from the switch-hook at telephone T7 aconductive path lwill ensue, operatively energizing the relay 436. A locking circuit can now be traced from grounded off-normal spring 437 of the off-normal set VR4 (which set operates on the first vertical or rotary off-normal movement of the shaft), armature 438 to the outer winding of relay 436. The said ground t is extended over conductor 439 to the upper winding terminal of the lower Winding -of back-bridge relay 440. Armatures431 and v 435 being attracted, the traced circuit including the telephone T7 will now include conductor 441, lower winding of relay 440 to the traced ground, and from the upper winding terminal of relay 440, conductor 442 to armareciprocate the relationship of the trunk con- N' with relation to the windductors 84 and 83 ings of relay 403, so that the current traversing the talking conductors of the trunk and the calling telephone will be reversed in direction. The said reversal hasno operative object in trative of the'present invention, wherein the equipment at the main office, so far as the calling telephone is concerned, is not novel. However, well known equipment (and as referred to in the cited may be substituted for the calling telephone, or be an adjunct thereof, susceptible to current reversal, and under that condition may visually evidence to the callingparty that a response has been party at telephone A'and the called party (the attendant) at telephone T7 are now in talking relation, conductors 402 and 442 being joined through condenser 442', and conductors 404 and 441 being joined through condenser 441.

Assume that the telephone T7 is busy when bank contact 710 is encountered-by wiper 702, and bank contact 710 therefore constitutes ground potential received from a wiper corresponding to 7 02, for example, in the manner as hereinbefore described consequent to the seizure thereof. Under the last assumed condition a circuit can be traced from ground on bank contact 710, wiper 702, conductor 426, sideswitch wiper 425 in second position to the inner winding of the private magnet P4, maintaining the private magnet actuated after the retraction of armature 427, and,

therefore, restraining the sideswitch wipers 418 and 425 from advancing into theirl third position. Interrupter relay 420 will deactuate following the retraction of the armature of the rotary magnet R4 resultant tothe said relay 420 interrupting its circuit. A circuit 12o can now be traced from grounded armature 427, armature428, armature 429, conductor 414, armature 415, winding vof therotary magnet R4, sideswitch wiper 418 in second position to grounded batter net operating to advance the wipers 701 to 704 an additional rotary step, in the manner as before described, thevsaid wipers now engaging bank contacts 720 to 723, respectively.

Assuming for the present that the telephone 13o which ground is 76 the specific system described illus- 85 patent to N ewforth) v90 obtained. The Calling 95 y, the rotary mag- 'element J will seize in t T7 is idle, and that, therefore, bank contact 721 and its electrically tied contact 720- and their multiples accessible to other switches do not constitute ground potential, the main e manner as before described wherein the connection was'effected to telephone T7. The ringer 725 of telephone T7 will be vibi-ated in the manner as before described with relation to the call to telephone T7', and the said main element J will function as before described with relation to telephone T7 upon the receiver at telephone T7 being removed from tlie switchhook. The telephone T7 may be assumed as one of the general telephones of the private automatic exchange, and, therefore, may or may not be located within physical reach of the attendant, in fact, may be responded to by some other party located remotely. Inasmuch as the telephone T7 would only be reached by the main element J when operating on its normal level if the telephone T7 is busy, it serves as a supplemental attendants station. As will appear presently, if the telephone T7 is also busy, the calling party at telephone A will receive a busy tone indicative of the busy condition. However, it will be manifest that an additional one or more telephones may be similarly related to telehone T7 with successive sets of bank contacts so that any one of a larger number thanv one telephone (as T7) may serve as auxiliary attendants stat-ions.

It will be assumed that when wiper 02 engages bank oontact 721 that it and itsL tied contact 720 constitute ground potential due to the line leading to telephone T7 being busy. Upon Wiper 701 encountering bank contact 720 a circuit can be traced from the said assumed grounded contact, wiper 701, conductor 448, make-before-break spring 449, armature 450, winding of busy relay 451, sideswitch wiper 418 to grounded battery, relay 451 actuating and locking through its armature 452 to grounded off-normal spring 437. The outer winding of the private magnet P4 is energized and locked to armature 452 by way of spring 453, and it will appear that relay 451 cannot unlock until ofi-normal spring 437 disengages, which can only occur when the shaft of the main element J restores to normal. During the time that relay 451 is actuated, ground-seeking tone source T5 is applied over conductor 501, through .armature 454, to talking conductor 441, audible to the calling party at telephone A. The calling party being thus apprised of the busy condition, wherein the call will not be responded to, will replace the receiver on the switchhook, thereby opening the energizing circuit traced for relay 403, whereupon the latter relay and its dependent relay ate. A circuit can now be traced from grounded armature 424, conductor 456, ofi'- normal spring 457 to the release magnet R64,

408, will deactu-` wanted is at tele hone T8, the local telephone number of whic is 12, The attendant at telephone T7 will manipulate the calling device on the said telephone in accordance with the first digit 1, whereupon relay 440 will deactuate and reactuate one time responsive thereto. At the time of the said deactuation a circuit can be traced from grounded armature 443, armature 458 (relay 444 sustainin over the lapse) conductor 459, winding o slow-releasing series relay 502, winding of vertical magnet V5, sideswitch wiper 503 to grounded battery, the vertical magnet operating one time to raise the shaft carrying wipers 801 to 803 one vertical step into alignment with the first level of bank contacts. At the time the vertical magnet operates, relay 502 operates and applies ground from its armature 504 through make-before-break spring 505 to the windin of the private magnet P5, causing the said private magnet to operate preparatory to permitting the sideswitch wipers 503 and 506 to advance into their second position consequent to the retraction of armature 504 following the operation of the vertical magnet. In this connection it will be noted that upon the actuation of relay 502 its armature 508 applies ground to the inner winding terminal of relay 436, over conductor 439, which would cause the said relay to actuate and lock were it .not in the present instance already locked. The object of the latter described function will appear presently. The attendant at telephone T7 Will now manipulate the calling device thereat in accordance with the second digit 2, whereupon relay 440 will deactuate and reactuate two times responsive thereto, its armature 443 applying two ground impulses through armature 458, conductor 459, winding of relay 502, armature 509, winding of rotary magnet R5, sideswitch wiper 503 in second position, to grounded battery, the rotary magnet operating two times to advance the wipers 801 to 803 two rotary positions into engagement with bank contacts 805 to 807, respectively. The relay 502 actuates coincident with the first impulse applied to the rotary magnet R5 and sustains until after the second impulseterminates. When relay 502 actuated it reenergized the private magnet P5, preparing it to release upon the retraction of armature 504, to permit the sideswitch Wipers 503 and 506 lto advance into their third position, the latter, in this instance, occurring following the said engagement of bank contacts 805 to 807. A circuit can now be traced from ground, sideswitch wiper 506, winding ion now be trace The said ground is extended over conductor of relay 510, sideswitch wiper 503 to grounded battery, seizing relay 510 actuating by way of accomplishing the seizure of the auxiliary element K. The ringing circuit can now be tracedfrom source G5, armature 512, armature 513, conductor 514, wiper 802, bank contact 806, conductor 810 through the ringer of telephone T8, conductor 811, bank contact 807, wiper 803, conductor 812, amature 515, armature 516 to the inner winding of ring-cut-of relay 517 to grounded battery, the ringer at telephone T8 vibrating responsive to the current from source G5, but the relay 517 is inoperative thereto. Upon the response wherein the receiver is removed at telephone T8 a conductive path will ensue, operatively energizing the rela 517. A locking circuit can from grounded off-normal spring 518 of the olf-normal set V05 (which set operates on the first vertical oli-normal movement of the shaft), conductor 519, armature 520 tothe outer winding of relay 517.

521 to the upper winding terminal ofl the lower winding of back-bridge relay 522. Armatures 513 and 515 being attracted, the described circuitincluding the telephone T8 will now include conductor 523, lower winding of relay 522 to the traced ground, and from the upper winding of relay 522, conductor 524 to armature 512, relay 522 actuating. A circuit can now be traced from grounded armature 527 to the winding of rslow-releasing relay 528, the latter relay actuating.

The object of the latter function will appear presently. vThe talking circuit traced to-conductors 406 and 306 is continuedv through armatures 460 and 461, conductors 462 andA 463, andV condensers 531 and 532 toconductors 524 and 523 respectively, so that telephones A, T7', andTS mutually.

At the time'the receiver was removed at telephone T8, and relay 528 actuated responare in talking relation sive thereto, bearing in mind that relay 444 was actuated due to the receiver being ofi the switch-hook at telephone T7',a circult can be traced from grounded armature 535, conductor 536, armature 464, conductor 465 to the winding of interrupter I5. The interrupter I5 is designed to operate its plungerarm 537 retardedly tolink its `contacts 538 and 539 for a brief predetermined period and then disengage them incidental to the continued upward stroke vof the plunger-arm, so that under the conditions of the contactsI 538 and 539 being linked the ground-seeking tone source T5 will be applied over conductor 540 to conductor 463 audible to the calling party at telephone A and also the first called party at telephone T7', as well as the second called party at telephone T8. v As stated, this tone being applied for a predetermined brief period serves to prompt the party at tele- Armai ture 529 applies its ground to conductor 446.l

.447 is'maintained loc presently, wherein the shaft phone T8,'who responded last, that not only' 1s the calling party at telephone A. in talking relation with said party at telephone T8, butl that a telephone as T7 for example, is also in talking relation with said party at telephone `T8,-and the calling party at telephone A, mutually. It is manifest in view of the traced circuits that if the telephone T7 were not in on the connection the armature 464` would be retracted, and, therefore, the described circuit energizing the interrupter I5 would not have been energized to apply the tone T5', and, therefore, the last party to respond, in this case the party at telephone T8,

.phone T8., `terminate' yconnection by replacing the-receiver thereat, relay 444 or relay 528, asthe case may-be, will deac'tuate and open the described energizing circuit of the interrupter I5, whereupon its plunger-arm will retract somewhat faster than it originally attracted', and again link the contacts 538 and 539, however, more-briefly than before, to apply the tone. source T5 audible to the remainingl two parties to the connection, thus apprlsing them that the third party to nectionv has disconnected therefrom. While abattery-click 4would' undoubtedly be discerne'dincidental to the .party disconnecting, this would not be positive information as would the' specific tone.

In this connection attention .v is directed the conthat when relay 447 actuated consequent to I from conductor 467 and extends to spring 545 of off-normal set V05, so that if the Shaft of main element J has restored to normal and the shaft of auxiliary element K has I.

operated' olf-normall The same would hold true, as will appear of main lelement Y beforehand the relay ed through spring'545.,

J will operate 'of-no'rmallyin a second false r operation before thev shaftef auxiliary elementv K restores tonormal, so that regardless of which element -J orK hasv itsshaft ot'- normal, or if bot-.h shafts are coincidentally olf-normal, the relay 447 locked.` However, the relay 447 will` become unlocked and deactuate, thereby establishing y the prlmary relation of the leading-incon--- will be maintained ductors 406 and 306 with the upper winding terminal and the lower winding terminal of relay 403, respectively, upon both the shaft of main element J and the shaft of auxiliary element K restoring.

Going back for a moment to the condition ensuing after -the talking connection was established between calling telephone A and telephone T7 and wherein the party at telephone T7 caused the auxiliary element K to be directively operated therefrom to set its wipers 801 to 803 into engagement with bank contacts 805 to 807, respectively, by way of passing the connection. It will be assumed that after the last foregoing described operation was completed, and before a response was obtained from the party at telephone T8, as hereinbefore described, the party at telephone T7 replaced the receiver on the switch-hook. Relay 440 will deactuate by reason of its energizing circuit being open at the switch-hook of telephone T7 and its dependent relay 444 will deactuate in sequence.l A circuit can now be tracedl from grounded armature 443, armature 458, to the winding of slow-releasing relay 470, the latter relay actuating. Then, upon armature 445 retracting immediately following the actuation of relay 470 and while relay 470 is still actuated due to its sloW-releasingcharacteristic, a circuit can be traced from grounded armature 445, armature 471, conductor 472, armature 546, conductor 547, offnormal spring 457 to the release magnet R64, the release magnet operating to restore the shaft of the main element J to normal. However, since the off-normal spring set V05 is operated, relay 447 will be maintained locked andthe telephone T8 will be signaled as before described wherein the party at telephone T7 retained connection, and the calling party at telephone A will be in talking relation with the last called party at telephone T8 upon the response thereat as in the instance before described, although in this instance the telephone T7 is not concerned, and, furthermore, the shaft of main element J is at normal, however, relays 447, 403, and 408 thereof are actuated, the relay 436 having unlocked incidental to the restoration of the shaft.

If, however, the party at telephone T7 in lieu of waiting until after the second digit 2 was sent and the relay 510 actuated to effect the seizure of the line leading to telephone T8, had replaced the receiver on the switch-hook before sending the second digit 2 and after sending the first digit 1, or at least replacing the receiver before the last impulse is sent and relay 510 actuates, a circuit is established from grounded armature 445, armature 471, conductor 472, armature 546, conductor 550, olii-normal spring 551 to release magnet R the release magnet operatingr to restore the shaft of auxiliary element K to normal. The party at telephone is to enable an error in calling a wrong digit,

or otherwise, to be effaced.

Assume that the line leading to telephone' T8 had been seized and rung upon, and perhaps no response obtained. In that event the relay 510 would be actuated. To effect the restoration of the shaft of auxiliary element K the party at telephone T7', will send digit l from the calling device thereat, whereupon relay 440 will deactuate and reactuate one time responsive thereto. Upon the said deactuation the relay 470 will be caused to actuate as hereinbefore described, then upon the reactuation of relay 440, armature 476 will apply its ground to armature 477 before relay 470 deactuates, the said ground being continued over conductor 478, armature 552, conductor 550,0-normal spring 551 to the release magnet R65, the release magnet operating as before, to restore the shaft of the auxiliary element K to normal.

Assume that at the time of calling telephone T8, as described, it is busy, and by rea.-

son of it having been previously engaged by a switch having access to it through one of the multipled contact sets, or perhaps due to a call having been initiated outgoing from the said telephone T8, so that the bank contact 805 engaged by wiper 801 constitutes ground potential. A circuit can now be traced from the assumed grounded Acontact 805, wiper 801, conductor 553, sideswitch wiper 506 in second position, make-beforc-brcak spring 554. winding of relay 555, make-before-break spring 505 to the winding of private magnet P5, the private magnet being maintained actuated because this circuit ensues upon armature 504 retracting. Under this condition the sideswitch wipers 503 and 506 are restrained against advancing into their third position, and, therefore, an operative circuit for relay 510 is not established, so that the auxiliary element K does not seize. Relay 555 will actuate and lock by way of its armature 556 to grounded off-normal spring 518, and will be maintained locked until the shaft of the auxiliary element K restores to normal. Incidental to the operation of relay 555, busy tone is applied from source T5 over conductor 501, armature 557 to talking conductor 523, audible to the calling party at telephone A and to the passing party at telephone T7 If it is desired to call an alternative telephone, the shaft of auxiliary element K can be restored by the party at telephone T7, sending digit l, whereupon a ground will be applied to conductor 47 8, in thc mannclas before dcscribcd,and continued 

